This competitive renewal application seeks continued support of an Immunoassay Core Laboratory within the Diabetes Research and Training Center of the Washington University School of Medicine. The overall purpose of the Core Laboratory is to support independently funded diabetes research by providing reproducible measurements of hormones, peptides, metabolites and amino acids in a cost effective manner. The laboratory measures total human insulin immunoreactivity, specific levels of human insulin (i.e. nonreactive with proinsulin), rat insulin, human C-peptide, rat/mouse C-peptide, human glucagon, human pancreatic polypeptide, human growth hormone, human IGF I, cortisol, human leptin, sensitive human leptin, mouse/rat leptin, glucose, beta hydroxybutyrate, lactate, and alanine. These services are provided in response to the documented research needs of 38 NIH-funded Washington University principal investigators and eight investigators at other institutions. The laboratory maintains accreditation from the College of AmericanPathologists, provides consultation services and assists in the laboratory training of residents, fellows, and established investigators.